<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<input type="button" value="write" onclick="document.write('abc')">
<!--document.write()功能是，写在页面上，先清空页面上的内容，再书写-->
</body>
</html>